Desk chair mat

ABSTRACT

A desk chair mat has a substantially planar upper surface suitable for interaction with a chair support structure, a perimeter defining an outer edge of the mat, a lower surface parallel to the upper surface. An array of generally blunt ended and laterally elongated projections extends downwardly from the lower surface for engagement with a carpet. A decorative pattern is also formed on the lower surface that is visible through the upper surface. Each projection has a smooth end surface spaced below the lower surface by a distance sufficient to penetrate into the carpet pile. The array is generally a regular pattern of the projections that can be arranged at an angle with respect to each nearest neighbor to provide enhanced resistance to lateral movement of the mat with respect to the carpet to protect the decorative pattern from abrasion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention is a continuation-in-part of U.S. application Ser. No. 10/842,387 filed May 10, 2004, which is in turn a continuation-in-part of U.S. application Ser. No. 10/439,691 filed May 16, 2003.

BACKGROUND

The present invention is directed to chair mats and specifically, to chair mats typically used under desk chairs in order to protect an underlying carpet. In particular, the present invention relates to a chair mat having a decorative pattern and on which a chair, such as a desk chair, may be used without harming the decorative pattern.

Desk chair mats for office and home use are well known. Such a chair mat has a main portion on which the desk chair rolls, and can include a forward lip portion which is adapted to extend partially into a desk well, and on which the feet of the person sitting in the chair can rest. A desk chair mat that is to be applied over carpeting is typically formed of a semi-rigid plastic, and has an array of short, sharp spikes on an underside thereof, which hold the mat firmly in place on the carpeting. While desk chair mats can be made without any spikes, the mats tend to move relative to the carpet in response to movement of any desk chair on the top surface of the mat. Thus a carpet-engaging structure is deemed necessary to achieve satisfactory performance.

Such a desk chair mat is awkward to carry and/or otherwise handle due to its size, the semi-rigid nature of the material from which it is formed, and particularly with the spikes. Unless the chair mat is boxed or otherwise protected, the user typically carries the chair mat by gripping about one or two of the edges of the chair mat, often resulting in irritation if not injury to the hands, due to the spikes projecting from the underside of the chair mat.

Attempts have been made to solve these problems by making the chair mat foldable to thereby reduce its size for handling purposes. See, for example, U.S. Pat. Nos. 4,784,888; 5,073,428 6,183,833 and 6,284,341. Further, handles have been included as a portion of the chair mat to enable safe handling. See, for example, U.S. Pat. Nos. 6,177,165; 6,287,659 and 6,308,842. Generally, desk chair mats have been sold at office supply stores or distributors as opposed to retail stores, and to some extent, the handling problem was alleviated by boxing the chair mats individually or in groups prior to shipping. Chair mats are now being found increasingly in retail outlets, compounding the problem of safe handling. While chair mats can be boxed, the boxes add cost and are themselves unwieldy, and are therefore not necessarily desirable in the retail environment. Thus, with increasing retail activity, new display schemes are also required. The last mentioned patent includes the disclosure of a retail display system designed to facilitate safer handling of chair mats.

Even when supplied from a distributor in boxed form, the end user must remove the chair mat from the box and position it at its final destination, again, with some difficulty due to the physical attributes of the chair mat. Thus the opportunity for irritation if not injury to the hands, due to the spikes projecting from the underside of the chair mat continues even after purchase. Accordingly, there remains a need for a solution to the problem of transporting desk chair mats easily and safely from the point of manufacture through the point of stocking and display in a retail environment to the point of ultimate use.

Once situated for use, a typical chair mat tends to be positioned over carpeting. Such chair mats are typically made of a transparent or translucent plastic material. Thus, the underlying carpet on which the chair mat is placed is visible through the chair mat as are the structural details of the pattern of spikes that project down to engage the carpet. The chair mat generally does not make any separate esthetic contribution. Some attempts have been made to arrive at chair mats that contribute esthetically as well as provide protection for the underlying carpet, for example, the mat disclosed in U.S. Pat. No. 6,319,592 to Ney et al. The Ney mat consisted of a separately prepared graphics layer sandwiched between a rigid base layer and a rigid upper protective layer. Both the base layer and upper protective layer were bonded to the graphics layer with the aid of adhesives. The nature of the graphics layer or the underlying adhesives layer is such as to render the base layer invisible. The area of the carpeting under such a chair mat would also be rendered invisible. This has the effect of making the chair mat itself stand out from the remaining portion of the carpeting, which may not be desirable in many situations.

Accordingly, there remains a need for a desk chair mat that includes a decorative contribution that is not subject to surface wear and remains visible along with the underlying carpet. There is also a need for such a desk chair mat that includes a carpet engaging structure that is designed for safe handling. It is desirable that these features be incorporated in a single structure having other features that contribute to easy handling and reduced cost

BRIEF SUMMARY

A desk chair mat of the present invention is intended for interposition between a carpet upper surface and a chair, and can have a substantially planar upper surface suitable for interaction with a chair support structure that typically includes a plurality of wheels on the lower outside points of a spider. The desk chair mat has a perimeter defining an outer edge of the mat, and a lower surface parallel to the upper surface. The lower surface can include an array of blunt projections extending downwardly from the lower surface for engagement with the carpet. Each of the projections can have a smooth end surface spaced below the lower surface of the desk chair mat by a distance sufficient to penetrate into the carpet upper surface, typically by about 3 mm or more. The array of projections can be confined to a one or more selected areas of the lower surface. The array of projections can be distributed substantially continuously over the entirety of the lower surface. The array of projections resists lateral forces acting on the desk chair mat and thereby stabilizes the mat with respect to the carpet.

The array of blunt projections can assume any number of appearances. The blunt projections can be linear, angular or curved. The vertical cross-sectional aspect ratio of the blunt projections is greater that one in a first direction and less than one in a direction normal to the first direction so that the blunt projections are laterally elongated. The smooth end surfaces of the blunt projections can be generally parallel to the lower surface of the desk chair mat or arcuate. The smooth end surface of each of the blunt projections has an area sufficient to prevent penetration of the skin of someone handling the mat, which is believed to be at least about 8 mm². The end surface of each of the blunt projections is sufficiently smooth to prevent abrasion of the skin of someone handling the mat.

The blunt projections can be aligned in spaced linear arrays. The resistance to lateral forces can be enhanced by arranging the blunt projections in a regular pattern wherein each projection is situated at an angle with respect to each nearest neighbor. The resistance to lateral forces can also be achieved by arranging the blunt projections in rows with the projections in adjacent rows being situated at an angle to each other. The blunt projections can cover a majority of the lower surface of the desk chair mat, but need not extend to any given area including the perimeter. The distance between the blunt projections can vary considerably, but is typically between about 1 and 4 cm.

A desk chair mat of the present invention is preferably sufficiently transparent that any pattern in the underlying carpet is not hidden or concealed by the presence of the desk chair mat. The array of blunt projections can be incorporated into other decorative designs present on the lower surface of the desk chair mat that are also visible through the substantially transparent mat. The other decorative designs can be, for example, in the form of ridges connecting the blunt projections or islands surrounding the blunt projections. The decorative designs can include undulating or other periodic surface variations on the lower surface of the desk chair mat that are formed by modest regular variations in the thickness of the mat. The variations on the lower surface of the chair mat can be formed during the extrusion-fabrication process by including an embossed or etched pattern on a pattern roll that is brought into intimate contact with the lower surface of the mat.

A desk chair mat of the present invention can be made from a suitable semi-rigid substantially transparent plastic such as acrylic, polycarbonate, polypropylene, or polyvinylchloride. The plastic preferably has a Rockwell hardness of between about 80 and 95, and can include static-reducing elements so long as the presence of such static-reducing elements will not significantly reduce the transparency of the mat. A desk chair mat of the present invention can include handles and tab structures that will facilitate the handling and display of the mat. A desk chair mat of the present invention can also include one or more fold lines or cuts that will enhance ease of handling. A graphic can also be included, for example, by contacting a second selected area of the chair mat lower or upper surface with a silk screen mat, a print transfer roll, a label, a decal, or other indicia bearing sheet or transfer roll. The first surface can remain un-affected by the application of the graphic so that the chair mat is generally transparent except where the subject matter of the graphic sufficiently inhibits the view of the underlying carpet.

One advantage of a desk chair mat of the present invention is a reduction in damage to the underlying carpet since the characteristic feature of the smooth end structure of the blunt projections that inhibits irritation and injury to the hands also protects the carpet. Another advantage of a desk chair mat of the present invention is a desk chair mat that can be produced at comparatively low cost yet can contain attractive decorative features on the lower surface of the mat that are protected from wear and visible through the substantially transparent mat. Other features and advantages of a desk chair mat of the present invention will become apparent to those skilled in the art from a consideration of the following discussion that makes reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the upper surface of a desk chair mat of the present invention, with certain features present on the lower surface being visible through the mat due to its substantial transparency.

FIG. 2 is a sectional view taken along line 2-2 of the desk chair mat of FIG. 1 with the desk chair mat being placed on a typical conventional carpet.

FIG. 3 is a detail perspective view of a portion of the lower surface of a desk chair mat showing several blunt projections of the present invention.

FIG. 4 is a detail perspective view of a portion of the lower surface of another desk chair mat showing several blunt projections of the present invention.

FIG. 5 is a bottom plan view of a portion of a desk chair mat of the present invention.

FIG. 6 is a bottom plan view of a portion of another desk chair mat of the present invention.

FIG. 7 is a bottom plan view of a portion of another desk chair mat of the present invention.

FIG. 8 is a bottom plan view of a portion of another desk chair mat of the present invention.

FIG. 9 is another bottom plan view of a portion of another desk chair mat of the present invention.

FIG. 10 is another bottom plan view of a portion of another desk chair mat of the present invention.

FIG. 11 is another bottom plan view of a portion of another desk chair mat of the present invention.

FIG. 12 is another bottom plan view of a portion of another desk chair mat of the present invention.

FIG. 13 is a detail perspective view of a portion of another desk chair mat of the present invention.

FIG. 14 is a detail perspective view of a portion of another desk chair mat of the present invention.

FIG. 15 is a sectional view taken along line 15-15 of the desk chair mat shown in FIG. 14.

FIG. 16 is a detail perspective view of a portion of another desk chair mat of the present invention.

FIG. 17 is a sectional view taken along line 17-17 of the desk chair mat shown in FIG. 16.

FIG. 18 is a detail perspective view of a portion of another desk chair mat of the present invention.

FIG. 19 is a schematic illustration of a method for making desk chair mats of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a desk chair mat 10 formed of a planar, semi-rigid member (made from, e.g., PVC, polypropylene, semi-rigid vinyl or other suitable material) having four side edges 12, 14, 16 and 18, which define a major portion 20 of the chair mat 10. An optional extension portion 22 of the same material and thickness, projects or extends integrally from side edge 18, and is further defined by edges 24, 26, 28 completing the periphery 30 of the mat 10, which can include a tapered edge 42. The extension 22, as is well known, is designed to project into the well area of a desk (not shown), with the remainder of the chair mat 10 behind the desk and serving as the principal contact area for a desk chair (not shown) typically (but not necessarily) fitted with rollers or casters. The chair mat 10 for purposes of this invention, however, need not have an extension 22 of this type. The chair mat 10 can include one or more handles 34, which can project from any point on the periphery 30 of the mat 10, or can be formed within the periphery 30 by one or more openings 35. The chair mat 10 can also include one or more hang tabs 36 along one or more side edges of the chair mat 10, the hang tabs 36 being formed with holes or apertures 38 which enable the mat 10 to be suspended from display hooks or similar structures. Alternatively or additionally, one or more small holes 40 can be formed within the periphery 30 of the mat 10 to facilitate hanging.

An upper surface 32 of the chair mat 10 is generally smooth, as shown in FIG. 2, so as to interact with the supporting structure of the desk chair. The phrase “generally smooth” in reference to the upper surface 32 is to be understood to include both smooth mirror-like surfaces and textured surfaces that resist scratches but remain sufficiently planar as to not significantly distort or hide the appearance of the lower surface of the chair mat 10 as viewed through the upper surface 32. The upper surface 32 of the chair mat 10 can also be formed with a tapered marginal edge 42 that extends about the entire periphery 30 of the chair mat 10 as shown in FIG. 1. The chair mat 10 also has a lower surface 44 that includes an array of laterally elongated, blunt ended projections 46 extending downwardly from the lower surface 44 for engagement with an underlying carpet 48. The lower surface 44 of the chair mat 10 can also have a graphic image or other decorative design 49 that is visible through the upper surface 32. The graphic image or decorative design 49 can be positioned merely in one or more selected portions of the chair mat 10 or can be located continuously across the entire lower surface 44. The area a graphic image 49 can be generally devoid of the projections 46. However, where the decorative design 49 extends substantially continuously across the entire lower surface 44, the projections can 46 typically be incorporated into and become part of the decorative design 49. The distribution of the laterally elongated projections 46 should be sufficient to ensure that the graphic image or other decorative design 49 will be adequately protected from abrasion by any underlying carpet. A graphic image 49 can be formed by a variety of techniques including silk-screening or otherwise printing an image directly onto the lower surface 44. A graphic image 49 can also be formed by applying a label or decal to the lower surface 44. The other decorative designs 49 are preferably formed by molding the design features the lower surface 44. The molding of the design the lower surface 44 can be accomplished during an extrusion process detailed below in connection with FIG. 19.

The laterally elongated, blunt ended projections 46 can include a smooth end surface 50 spaced below the lower surface 44 by about 3 to 10 mm. In cross-section, as seen in FIG. 2, the projections 46 can have a height to width aspect ratio between about 2 and 4 that enables the end surfaces 50 of the projections 46 to nestle into the pile 52 of the carpet, generally without contacting the carpet backing 54. A light phantom outline of a side view of another of the laterally elongated, blunt ended projections 46 is shown partially hidden by the pile 52 of the carpet 48. The projections 46 are shown in FIG. 2 to extend downward from a generally planar lower surface 44 that can include a decorative pattern 49 generated by a generally regular array of valleys 47 and/or ridges 45, which are discussed in greater detail in connection with FIGS. 13-18

Some typical laterally elongated, blunt ended projections 46 on lower surfaces 42 of a chair mat 10 of the present invention are shown in greater detail in FIGS. 2 and 3. It will be noted initially that FIG. 4 includes a section line 2-2 that indicates the direction of the cross-section shown in FIG. 2. It will be further noted that the projections 46 typically comprise a pair of generally parallel sidewalls 56 and 58 that project essentially normally from the lower surface 44 of the mat 10. The end surface 50 of the projections 46 extend from one sidewall 56 to the other sidewall 58. The end surface 50 can be arcuate as shown in FIG. 3 or more flattened as shown in FIG. 4. When the end surface 50 is flattened as shown in FIG. 4, the projections 46 also include tip surfaces 60 which are shown to be rounded but can also be flattened. It is desirable that the ends 50 are not pointed or sharp so that injury to both the installer and the carpeting is avoided. To achieve the desired bluntness, the area of the end surface 50 is generally at least about 8 mm².

The laterally elongated, blunt ended projections 46 can be arranged in a variety of patterns. Further the projections 46 can take a variety of individual shapes. Both FIGS. 3 and 4 show the projections 46 arranged in a rectangular array, which can be, for example, linear or square. The term “square” when used in characterization of an array or projections is intended to include circumstances wherein each projection 46 forms merely a small elemental portion of the rectangle and the corners 62 of the rectangle are defined by some imaginary points located at the intersection of lines 64 projecting length wise from the tip surfaces 60.

A variation on this rectangular array is shown in FIG. 5 in which parallel rows 66 of the linearly elongated blunt ended projections 46 are arranged so that the tips 60 of the individual projections 46 are perpendicular to the sides 56 and 58 of adjacent projections 46, which results in a staggered rectangular array. The projections 46 of the array shown in FIG. 5 are somewhat closer to each other than are the projections of the arrays shown in either FIG. 3 or 4. As a rule, the distance between nearest neighbor projections 46 is generally between about 1 and 4 cm. If the spacing is dramatically smaller that this, the mat 10 can tend to ride on top of the carpet 48 rather than nestle into the pile 52 as preferred. If the spacing is dramatically larger that this, and the size of the individual projections 46 remains substantially unchanged, the laterally elongated side surfaces 56 and 58 may not provide sufficient stability of the mat 10 relative to the carpet 48 to prevent creep, which can lead to abrasion of the lower surface 44 that may limit visibility of and otherwise detract from the image or other decorative design 49.

A further variation on this rectangular array is shown in FIG. 12 wherein some of the laterally elongated, blunt ended projections 46 are connected to or incorporated within ridges 45 of sufficient length continuously along the lower surface 44 to individually define a closed loop 43 such as a rectangle, square, circle, parallelogram, trapezoid, or other irregular figure. The shape of the closed loop can be selected, for example, to coordinate with an underlying carpet pattern. The closed loops 43 can be arranged concentrically about central points 41, which in turn can be arranged in arrays of various decorative designs 49. The closed loops 43 have the added advantage of contributing significantly to the structural rigidity of the chair mat 10 in which they are incorporated. This added structural rigidity can be used to reduce the thickness of the mat 10 thus lowering its material cost, while retaining the desired performance. This added structural rigidity can also be limited for use in critical areas of the mat that typically bear larger deformation forces or for special “heavy weight” models. FIG. 13 shows a further variation on the rectangular array shown in FIG. 12 wherein some of the laterally elongated, blunt ended projections 46 are connected to and incorporated within the intersecting junctions 86 of the ridges 45, which define a closed loop 43 shown to be, for example, a rectangle or square, forming a decorative design 49 that is visible through the substantially transparent chair mat 10.

The arrays of the projections 46 need not be rectangular. For example, in FIGS. 6 and 7, the bottom surfaces 44 of mats 10 with two different arrays wherein the projections 46 are arranged in a non-perpendicular manner with respect to each other. In FIG. 6 the projections 46 are arranged in rows 68 of parallel projections 46. The projections in adjacent rows 68 are arranged at angle of about 60° with respect to each other and aligned so that the projections 46 in adjacent pairs of rows appear as a series of chevrons that are missing a middle portion. In FIG. 7, the projections 46 in each row 70 alternate orientation by an angle of about 60° so that the overall pattern defines a series of diamonds 72 outlined by the projections 46, the corners of the diamonds being located midway between the rows 70 of projections 46. The non-rectangular arrays of projections shown in FIGS. 6 and 7 still provide the desired lateral stability to the mat 10 when placed on a carpet 48.

FIG. 8 shows yet another arrangement of the laterally elongated, blunt ended projections 46 on the bottom surface 44 of a mat 10 of the present invention that involves alternating rows 74 and 76. The projections 46 in rows 74 are placed in an alternating angular pattern with the angle between adjacent projections 46 being about 90°. The projections 46 in rows 76 are all parallel with each other, and arranged parallel to one of the two sets of projections 46 in row 74. Examined diagonally, it will be seen that the projections 46 are arranged in pairs with a first two projections being situated in a first orientation and the next two projections being situated at 90° to the first orientation.

FIGS. 9 and 10 show the bottom surfaces 44 of mats 10 with two different arrangements of the projections 46, wherein each of the laterally elongated, blunt ended projections 46 is an arcuate element having an outside surface 78 and an inside surface 80 joined by rounded tip surfaces 60. In FIG. 9 the projections 46 arranged in rectangular sets 82 of four projections in each set. The sets 82 are then situated in a rectangular array. In FIG. 10, the arcuate projections 46 are arranged in diagonal rows 84 with the arcuate projections in each row alternating in orientation by 180°.

FIG. 11 shows the bottom surfaces 44 of mat 10 having an arrangement of laterally elongated, blunt ended projections 46, wherein each of the projections is a doubly curved element in the form of an S. The arrangement of the projections 46 shown in FIG. 11 is similar to the arrangement shown in FIG. 5, but the rows 66 are perpendicular rather than diagonal. Mats 10 having the non-linear projections 46 shown in FIGS. 9-11 may be less apparent to the casual observer when situated on a carpet having a complex pattern than mats with the more linear elements shown in FIGS. 5-8, and may thus contribute to a given office appearance. Alternatively, arrays of parallel linear projections that are suitably spaced from each other can also contribute to a very official appearance while achieving the desired stability of the chair mat. The selection of linear or non-linear projections 46 can be coordinated with other features of any other decorative pattern 49 present on the bottom surface 44 of the mat 10.

FIGS. 14 and 15 show an example of a desk chair mat 10 of the present invention in which each of the laterally elongated blunt ended projections 46 are incorporated within a generally circular or oval ridge 45. Each ridge 45 can be separated from any adjacent ridge 45 by a planar portion 88 of the bottom surface 44. The height of the ridges 45 is small by comparison to the height of the projections 46. The lateral dimension of the projections 46 is generally smaller than the ridges 45 so that the ends of the projections 46 are spaced from the edges of the ridges. When viewed through the substantially transparent mat 10, the decorative pattern 49 that is generated by the structure shown in FIGS. 14 and 15 can be characterized as appearing as an array of cat-eyes.

FIGS. 16 and 17 show an example of a desk chair mat 10 of the present invention in which each of the laterally elongated, blunt ended projections 46 are incorporated with a generally linear ridge 45, however not all of the ridges 45 incorporate blunt projections 46. The ridges 45 can be seen to be arranged in a parallelogram fashion with respect to each other to generate a decorative pattern 49 that can be seen through the substantially transparent mat and generally described as a basket weave design that can be considered an enhancement of the design shown in FIG. 7. Each ridge 45 can be separated from any adjacent ridge 45 by a valley 47 or a planar portion 88 of the bottom surface 44. The height of the ridges 45 is generally small by comparison to the height of the blunt projections 46. The length of the projections 46 is generally smaller than the ridges 45. The widths of the projections 46 can be substantially equal to the widths of the ridges 45 as is also shown in the case of FIGS. 12 and 13.

FIG. 18 shows the lower surface 44 of a desk chair mat 10 of the present invention in which the decorative pattern 49 itself has sufficient vertical relief to comprise an array of laterally elongated, blunt ended projections 46 extending downwardly from the lower surface for engagement with any underlying carpet. Each of the laterally elongated, blunt ended projections 46 are positioned perpendicularly to ridges 45 that are staggered with respect to each other. The projections 46 can also be characterized as defining a slip line 51 between the offset valleys 47. The projections 46 are distributed substantially continuously throughout the design feature 49 generated by the combination of the ridges 45 and valleys 47.

One convenient method for manufacturing the mats 10 of the present invention is illustrated schematically in FIG. 19. A suitable polymer is introduced into inlet 186 of extruder 188 typically in pellet form. The extruder 188 heats and works the polymer in a well know fashion to form a continuous stream 189 of plastic that exits outlet 190. The outlet 190 is situated adjacent to a nip region 192 between two generally cylindrical rollers 194 and 196. The position of the upper roller 194 with respect to the main roller 196 can be controlled to define the width of the nip region 192 which also controls the thickness T of the web 195 and the mats 10 formed by the process. In accordance with the present invention, the main roller 196 includes a surface 197 formed, for example, by machining, etching, engraving or carving to include indentations for defining the projections 46 present on the lower surface 44 of the chair mat. The surface 197 can also include indentations or projections reflecting any additional graphic images and decorative features 49 that are desired to be created on the lower surface 44 of the chair mat 10.

A take-off roller 198 is positioned below the main roller 196 to ensure that the extruded plastic web 195 is retained in contact with the surface 197 of the main roller 196 for sufficient time to “freeze” the features of the projections 46 and decorative features 49 into the plastic of the chair mat 10. The take-off roller 198 can also be used in conjunction with an application roller 200 and an ink roller 202 to apply an optional printed graphic image to the bottom surface 44 of the web 195. The take-off roller 198 can also be used in conjunction with application roller 200 to apply a label or decal 201 from a supply roller 204 to the bottom surface 44 of the web 195. The take-off roller 198 can also direct the extruded plastic web 195 through a nip 206 between cutting rollers 208 and 210 that can be used to separate the chair mats 10 from each other and from any waste portion 199 of the web 195. The position of the cutting rollers 208 and 210 with respect to the various areas containing, respectively, the projections 46 and decorative features 49 can be controlled by a synchronizing means 212 such as a timing belt or an optical sensor and control. The desk pads 10 can then be conveyed by conveyor 214 for additional processing and packaging, if desired.

The foregoing detailed description should be regarded as illustrative rather than limiting, and the following claims, including all equivalents, define the spirit and scope of this invention. 

1. A desk chair mat for interposition between a carpet and a chair, the desk chair mat comprising: a substantially transparent body having a generally planar upper surface suitable for interaction with a chair support structure, a perimeter defining an outer edge of the body, and a lower surface generally parallel to the upper surface, the lower surface including a decorative pattern that is visible through the upper surface and an array of laterally elongated projections having blunt and smooth end surfaces extending downwardly for engagement with any underlying carpet.
 2. The desk chair mat of claim 1 wherein the smooth end surface of each of the projections is generally parallel to the lower surface.
 3. The desk chair mat of claim 1 wherein a horizontal cross-sectional aspect ratio of each of the projections is between about 2 and
 4. 4. The desk chair mat of claim 1 wherein the smooth end surface of each of the projections has an area of at least about 8 mm².
 5. The desk chair mat of claim 1 wherein the smooth end surface of each of the projections is spaced from the lower surface by about 3 to 10 mm.
 6. The desk chair mat of claim 1 wherein the projections are arrayed such that each projection is spaced from its nearest neighbor projection by between about 1 and 4 cm.
 7. The desk chair mat of claim 1 wherein a vertical cross-sectional aspect ratio of the projections is greater than one in a first direction and less than one in a second direction.
 8. The desk chair mat of claim 1 wherein the array comprises a regular pattern of projections arranged at an angle with respect to each nearest neighbor.
 9. The desk chair mat of claim 8 wherein the angle is at least
 300. 10. The desk chair mat of claim 1 wherein some of the projections are connected to each other with ridges that extend from the bottom surface by a distance less than the blunt projections.
 11. The desk chair mat of claim 1 wherein the decorative pattern extends continuously over the entire lower surface.
 12. The desk chair mat of claim 1 wherein the decorative pattern extends over only a selected portion of the lower surface.
 13. The desk chair mat of claim 1 further comprising at least one opening within said perimeter forming a handle for the mat.
 14. A desk chair mat for interposition between a carpet and a chair, the desk chair mat comprising: a semi-rigid sheet of plastic having a substantially planar upper surface suitable for interaction with a chair support structure, a perimeter defining an outer edge of the mat, a lower surface parallel to the upper surface, the lower surface including a decorative pattern that is visible through the upper surface and an array of laterally elongated, blunt ended projections extending downwardly from the lower surface for engagement with any underlying carpet, each projection having a smooth end surface spaced below the lower surface by a distance sufficient to penetrate into the carpet, the array being a regular pattern of the blunt projections arranged at an angle with respect to each nearest neighbor to provide resistance to any lateral movement of the mat with respect to the carpet.
 15. A method of manufacturing a desk chair mat for interposition between a carpet and a desk chair, the method comprising the steps of: providing a first roll having a surface including an array of cavities, coupling the first roll to a second roll to define a nip of selected dimension, extruding a stream of plastic into the nip under conditions ensuring that the array of cavities will be generally filled by the plastic to form a decorative pattern that is visible through the upper surface and an array of laterally extending, blunt ended projections on a first surface of a continuous web of plastic, defining a perimeter of a mat surrounding the first and second areas of the continuous web, and separating the mat within the perimeter from the continuous web.
 16. The method of claim 15 further comprising a step of creating a graphic image on the surface of the first roll.
 17. The method of claim 15 further comprising a step of creating a graphic image on the mat by printing the image on a surface of the continuous web.
 18. The method of claim 15 further comprising the steps of creating a graphic image on a separately formed web and bonding the separately formed image to a surface of the continuous web.
 19. The method of claim 15 further comprising the step of shaping the interior of the cavities to have a smooth truncated end surface capable of molding the smooth blunt ended projections.
 20. A desk chair mat for interposition between a carpet and a chair, the desk chair mat comprising: a semi-rigid sheet of plastic having a substantially planar upper surface suitable for interaction with a chair support structure, a perimeter defining an outer edge of the mat, a lower surface parallel to the upper surface, the lower surface including a three-dimension decorative pattern that is visible through the upper surface, the decorative pattern including sufficient vertical relief to comprise an array of laterally elongated, blunt ended projections extending downwardly from the lower surface for engagement with any underlying carpet. 